1981LT1

iTrader: (1)

So my fuel pressure is set to 45psi while the car is running but once I shut it down, the pressure starts dropping and within a minute, its down to 0psi. I'm not using the factory fuel pump assembly so there is no check valve to keep the pressure. Is there anything any of you have done to keep this from happening? It's rather embarrassing to crank my fuel injected car like it's got a carburetor that's not tuned. I've checked my injectors and they are not leaking down, so I can only assume the fuel is either bypassing the pressure regulator, or the pump. I just don't know if there's check valve or something I can put in the fuel system.

cprmn14

iTrader: (3)

Mines doing the same thing man, my first thoughts were injectors or FPR. When your car starts does it stay at 45 or do you loose pressure after ignition too?

Lonnie P

You need to post more info as I have no idea what pump & regulator you are using.

Most intank pumps have a check valve. If it doesn't you can easily add one to the supply line.

Some regulators bleed down rather quickly.

A slight intank leak (hose or connection) will drop pressure rather quickly.

TKR 88 GTA

I have a holley afpr (2nd one) doing the same thing I was able to narrow it down to the regulator by pinching off the return line while manual ly turning the fuel pump on and letting it build if there is pressure, it pretty much means your regulator isnt holding the residual pressure. They should at least be holding for 10 minutes at the least. Should be able to hold pressure with out dropping for about 12 minutes but loosing a couple should not matter. Just from my experience.

1981LT1

iTrader: (1)

Just so everybody knows, I'm running a 95 LT1 with a corvette in tank fuel pump and factory TPI fuel lines. The fuel pressure is steady at 45psi with the engine running but drops immediately after the car is shut off. I'm using a Holley afpr that I bought new. I've got almost the exact same setup in my 81 Camaro but I'm using an accel regulator. I have not swapped them out to do some troubleshooting but I think I may give that a shot if nobody has any other ideas

TKR 88 GTA

Mine does the exact same thing. Its holding no problem when engine is running. Try the pinching the return line method if pressure drops still its not your regulator its gotta be a check valve near the pump. If it holds the pressure while the return line is pimched then its bleeding past the regulator.

Prokilllsx

Sounds like issues with fuel pressure regulators. How many of you are using aftermarket ones because I hear they are bad for going bad in that area.

cprmn14

iTrader: (3)

Stock FPR. Mine goes from 45-0 psi almost instantly. I havent heard too many good things about aftermarket ones

TKR 88 GTA

I got the hsr intake so I have after market one my oe on the tpi never had issues lol

96BlownSSragtop

iTrader: (5)

The first combination that I built with Larry at ASSC Racing using a non-stock fuel pump arrangement had the exact same issue. When I called him with a concern about what was going on, the response was "who cares after the engine is shut off?" ...... fuel pressure only matters when the engine is running! The aftermarket pumps that I have in my car do not have a "back flow" type of internal valve so when I turn the key to the on/accessory position, let the pump built pressure, then turn the key to start the car ....NO issues. To date I've gone through 3 different combitations in 9 years (blown and n/a) with the same fuel pump arrangements with NO ISSUES!!!!

Just saying.....

cprmn14

iTrader: (3)

That may be true, but bottom line it should hold pressure steady for a few minutes, maybe it ran well but doesnt mean that you dont have an injector dripping etc. Were you running super lean?

TKR 88 GTA

Ya what cprmn14 said. Idk what the difference is between ours but when the OP says he has to crank the car like its an untuned carb that pressure drop to 0 should have something to do with it lol. I know thats my problem. If I turn my car off and try to start it right away it will sit there and want to crank even if I try to start it after the fuel pump primes.

1981lt1 is everything else working properly such as o2 sensor and no exhaust leaks what so ever ive seen exhaust leaks cause starting problems as well if the leak was before the o2 sensor

1981LT1

iTrader: (1)

Everything else is good. I'm going to try swapping the pressure regulator this weekend and see what happens.

86White_T/A305

fuel regulator..been there and done that lol. usualy its the diaphragm that goes bad and leaks pressure instantly after shut off. seen it happen with stock replacements and aftermarket regulators. big headache for a small/cheap part lol

JRobling

This is everything I had to do to fix it, combination of a bad pump and clogged filter: